Flotation process for reagent removal



United States Patent 3,331,505 FLGTA'IIGN PROCESS FGR REAGENT REMGVAL Vcnancio Mercade, Metuchen, N.J., assignor to Minerals 8.; Ihernicals Philipp Corporation, Woodbrid'ge, N.J., a corporation of Maryiand No Drawing. Filed Sept. 22, 1964, Ser. No. 398,376 20 Claims. (Cl. 209-711) This invention relates to the desorption of negative-ion flotation reagents from oxidized minerals and to the use of calcite to eifect such result.

One form of the invention is directed to the use of calcite to desorb fatty acid collector reagents in rougher flotation concentrates so as to permit further beneficiation of the concentrates.

Another form of the invention is directed to the selective froth flotation of calcite from oxidized minerals in bulk float products containing negative-ion flotation reagents.

Calcite, a mineral form of calcium carbonate, can be readily floated from alkaline aqueous pulps with a higher fatty acid collector reagent when the calcite is in a suitable degree of subdivision. Under similar flotation conditions, a great variety of other finely divided oxidized minerals can also be floated. Among these other oxidized minerals may be mentioned metalliferous oxides, silica and silicates. When sodium silicate is present in the pulps, silica and silicate minerals will be depressed. It is obvious that when an aqueous ore pulp containing finely divided calcite and also containing metallurgically significant quantities of finely divided metallic oxide minerals and/ or silica and metallic silicates is subjected to froth flotation in an alkaline circuit with fatty acid collector reagent, there will result a bulk float concentrate containing the calcite and the oxidized minerals. For many applications, the bulk float products can be used without separation of the calcite from the remaining constituents. This is true, for example, in cement production wherein high purity calcite products are not required and the presence of some siliceous matter with the calcite is desirable. This is not true, however, of certain other bulk float operations. For example, when manganese oxide or iron oxide ores containing gangue including an appreciable amount of calcite are beneficiated by flotation with negative-ion collector reagents, the calcite will report in the froth along with the manganese or iron mineral particles. In order to obtain manganese or iron concentrates of suflicient purity, the calcite must be removed.

So-called ultraflotation concentration is another example of a flotation operation wherein it may be desirable or, in some instances, necessary, to separate finely divided calcite from a flotation concentrate containing fatty acid collector reagent. Ultraflotation is a process for the selective froth flotation of ultrafine minerals or slimes. This process, which is described in an article by Ernest W. Greene and James B. Duke entitled Selective Froth Flotation of Ultrafine Minerals or Slimes, Society of Mining Engineers, pages 389 to 395, December 1962, extends flotation to the beneficiation of particles that are too fine for conventional flotation. The process entails the use of finely divided auxiliary mineral particles which are incorporated into the slirned ore pulp. Also incorporated into the pulp is a reagent to oil and float the auxiliary mineral particles and the desired mineral or minerals in the feed pulp. The auxiliary mineral particles act as a carrier for the floatable mineral in the feed pulp when a suitable oiling reagent is used. For this reason, the auxiliary particles are usually referred to as carrier particles. The process has been effectively applied to the beneficiation of many ores. When using a fatty acid oiling reagent in an alkaline pulp, as in the flotation of metal mineral, minus 325 mesh calcite has produced excellent "ice results as the carrier mineral. Obviously, in such a process it is desirable to separate the calcite carrier from the froth product in order to reuse the carrier in subsequent flotation operations. When a valuable mineral reports in the froth product of ultraflotation, as in certain metal oxide flotations, it is essential to separate the calcite carrier from the metal oxide in order to concentrate the metal oxide values.

A general object of my invention is to provide a method for desoroing fatty acid collector reagents from noncalcareous oxidized minerals.

One specific object of my invention is to provide a method for dereagentizing a fatty acid-reagentized rougher flotation concentrate containing noncalcareous mineral particles so that the concentrate can be further beneficiated.

Another specific object is to provide a method for selectively floating calcite from noncalcareous oxidized minerals in a fatty acid-reagentized bulk float concentrate containing both calcite and the noncalcareous minerals.

Still another object is to provide a method for separating slimed metalliferous values from a calcite carrier used to float these metalliferous values by ultraflotation concentration.

Briefly stated, this invention contemplates a novel method for desorbing fatty acid collector reagents from noncalcareous oxide and/ or silica and silicate minerals in a finely divided ore pulp. In accordance with this invention, the desired removal of fatty acid flotation reagent from the noncalcareous minerals is effected by heating an alkaline pulp containing noncalcareous minerals and fatty acid collector reagents with agitation in the presence of the combination of (l) finely divided calcite and (2) relatively large amounts of an alkaline dispersing agent such as sodium silicate. The heating with agitation is continued until the froth on the surface of the agitated pulp is clean and crystal-clear in appearance. The pulp is then aerated and a froth is withdrawn. The froth is a concentrate of calcite since the metal oxide and/or silica and silicate minerals are depressed and remain in the pulp. Flotation of the calcite is apparently caused by the deoiling of the noncalcareous minerals, with resulting overoiling and, therefore, flocculation and flotation of the fine calcite. The reason why the noncalcareous minerals are deoiled and depressed is not presently understood. It is known, however, that the presence of calcite in the dispersant-treated pulp in some way accounts for the depression of noncalcareous minerals since, in the absence of calcite, fatty acid reagentized noncalcareous minerals will still float after a high temperature dispersant treatment.

In accordance with one form of this invention, finely divided calcite is added to a rougher flotation concentrate containing fatty acid reagentized noncalcareous minerals for the purpose of removing the fatty acid reagent from the noncalcareous minerals. After flotation of the calcite additive, the remaining pulp can be subjected to further beneficiation with selective flotation reagents to obtain a higher grade concentrate of the noncalcareous mineral values in the original rougher concentrate. In this case, it is preferable to add minus 325 mesh calcite to the pulp before addition of the dispersant.

In accordance with still another form of this invention, finely divided calcite is a constituent of a fatty acid reagentized bulk float concentrate also containing noncalcareous oxidized minerals. In this case, the calcite, as well as the noncalcareous metal oxide and/or silica and silicates, contains the fatty acid collector reagent. Surprisingly, the fact that the calcite is already reagentized with fatty acid does not prevent the calcite from removing the fatty acid reagent from the noncalcareous minerals in the bulk concentrate.

At present, the second-mentioned form of my invention is of especial importance as it is applied to the separation of a calcite carrier from slimed noncalcareous oxidized metallic minerals, especially heavy metal oxide minerals, in ultraflotation froth concentrates. One class of slimed metal oxides to which this embodiment of my invention is applicable includes anhydrous oxides of tetravalent metallic elements, exemplified by cassiterite (SnO and anatase (TiO Minerals with surface characteristics similar to these minerals are rutile and zircon. As shown hereinafter, a calcite carrier was separated by flotation in substantially quantitative amount from slim-ed cassiterite in an ultraflotation concentrate by the practice of this invention. The recovered calcite carrier was substantially free from tin and was in a condition suitable for reuse in subsequent ultraflotation operations. Substantially all of the tin values in the ultraflotation concentrate were depressed and were recovered as a machine discharge product. It was interesting to observe that the required depression of fatty acid reagentized tin minerals could not be realized by means of the high temperature dispersant treatment when calcite was not present in the pulp. This phenomenon corroborated visual observation that collector reagent originally on the tin minerals was transferred to the calcite, causing controlled flocculation and selective flotation of the calcite.

My process will be more fully understood by the following description. In this description, certain flotation feed material will be referred to, for the sake of simplicity, as a bulk float material. It will be distinctly understood, however, that the term bulk float as used in this description and in the appended claims is intended to encompass ultraflotation concentrates, including ultraflotation concentrates which have received one or more cleanings, as well as bulk float products obtained by conventional flotation of ore pulps.

A typical bulk float concentrate used as a starting material in carrying out the high temperature dispersant treatment of this invention is a pulp which contains calcite and a noncalcareous metal oxide, especially a heavy metal oxide, or a noncalcareous metal silicate. Especially good results are realized with slimed pulps which are fine enough to pass a 200 mesh (Tyler) screen, and are usually fine enough to pass a 325 mesh (Tyler) screen. The process, however, is also useful in slimed pulps containing some coarse (e.g., plus 65 mesh) particles. The bulk flotation concentrates I treat contain a fatty acid collector reagent, e.g., crude or refined tall oil, oleic acid of animal or vegetable origin, lauric acid, sulfo-oleic acid or the like. Frequently, pulps of metal oxide minerals contain siliceous gangue, although when sodium silicate is used in obtaining the bulk float material the siliceous gangue is depressed and the quantity of silica and silicate in the float product may be small. The pH of the fatty acid reagentized pulps is usually on the alkaline side and must obviously be high enough to prevent decomposition of the calcite. In addition to the aforementioned ingredients, slimed bulk floats will contain a slime dispersant, usually sodium silicate, and frequently a mixture of sodium silicate and sodium carbonate. The pulps may also contain hydrocarbon oils and/ or other flotation reagents.

In putting this invention into practice, I usually prefer to filter the bulk float product and then adjust the solids of the filter cake by addition of a suitable amount of Water. Pulps of percent to 30 percent solids are suitable. To the pulp there is added a soluble dispersant in amount at least suflicient to disperse the pulp. The dispersant employed in my process can be any dispersant which is effective in an alkaline pulp. One class of dispersants includes alkali metal salts of condensed phosphates (e. g., sodium hexametaphosphates, sodium tripolyphosphates, tetrasodium pyrophosphate, sodium tetraphosphate and analogous potassium condensed phosphates). Another class is that of the alkali metal silicates. The preferred alkali metal silicate is sodium silicate having a mol ratio of SiO /Na O within the range of 2/1 4 to 3/1. 0 brand sodium silicate, which has a SiO /Na O mol ratio of 3/1 and contains 36 percent solids, is especially recommended. The sodium silicate, or other dispersant, can be added in stages, with agitation after each addition, or all of the dispersant can be added at once and agitated. The latter is preferred. A recommended quantity of sodium silicate is typically from 15 to pounds (anhydrous sodium silicate basis) per ton of solids present in the pulp. In a typical 20 percent solids feed pulp, the dispersant concentration will be in the neighborhood of 1 to 10 grams per liter, more usually 4 to 6 grams per liter, and the pH will be slightly less than 10.0, e.g., about 9.8 to 9.9. Addition of alkali, usually sodium hydroxide, to bring the pH to a value of at least about 9.0 may be necessary. Alkali can be added before or after addition of the dispersant, preferably before. The agitation of the pulp at elevated temperature can commence before or after addition of the dispersant is completed and is carried out without aerating the pulp. The pulp temperature during the agitation must be Within the range of from about F. to about 220 F. Excellent results have been achieved at about 180 F. to F. At temperatures appreciably below 150 F., e.g., temperatures of 80 F. and 120 F., the dispersant treatment is inefficient and separation of calcite from non-calcareous minerals is very poor as compared to the separation achieved when the treatment is carried out at higher temperatures. During the high temperature agitation of the dispersant-treated pulp, the froth on the surface of the pulp will initially be distinctly slimy, indicating the presence of finely divided particulate matter. As agitation is continued, typically after ten minutes, the froth will appear clean (nonslimy). This froth condition indicates that the heating has been of adequate duration. To insure a high temperature treatment of adequate duration, I prefer to continue the agitation and heating of the pulp after the froth initially presents the desired nonslimy apappearance so that the total time for the high temperature treatment usually ranges from about 15 minutes to about 2 hours. The pulp is now ready for aeration and flotation after dilution to a suitable solids level, typically 5 percent to 10 percent solids. No collector reagent, such as fatty acid or oil, is added to the pulp. Aeration and flotation can be carried out while the pulp is still hot or the pulp can be allowed to cool to ambient temperature before flotation. Dilution of the pulp before flotation obviously tends to cool the pulp considerably. With some highly alkaline pulps, it may be desirable to acidify the pulp slightly (e.g., bring the pH to a value from 9.0 to 9.5) after high temperature dispersant treatment and before flotation in order to promote controlled flocculation.

of calcite in the pulp. However, if too much acidifying agent is used and all of the pulp is flocculated, the use of the acidifying agent will be determined. In this case, metal oxide and/or any silica or silicates may be flocculated and float along with the calcite. This may occur when the pH is reduced to a value appreciably below 9.0, say 8.5. Thus, the selective flotation of the calcitemust be carried out at a pH of at least 9.0, preferably at a pH of 9.5 to 10.0. The froth product, which is composed largely of calcite, can be cleaned by reflotation to obtain a more pure calcite product and the various machine discharge products combined to recover the deoiled non-calcareous minerals in the form of an aqueous pulp. The composite machine discharge product, which may contain silica and silicates, can be further beneficiated, as by flotation with selective reagents, by gravity concentration, by chemical treatment, etc., to obtain a higher grade concentrate.

When my invention is applied to the deoiling of a rougher flotation concentrate that does not contain calcium carbonate minerals, the steps will be similar to those used in handling bulk concentrates, except that in the former case the calcite will have to be added to the fatty acid reagentized pulp. The addition of calcite can be performed before, during or after the high temperature sodium silicate treatment but must be present in the silicate-treated pulp while the pulp is still hot. No addition of fatty acid reagents is required since the calcite deoils minerals in the rougher concentrate and thereby becomes reagentized and amenable to air bubble attachment and flotation.

The examples which follow illustrate further the process of the present invention.

It will be distinctly understood, however, that my invention is not limited to the specific embodiments of the invention illustrated in the examples, for the principles of this invention are considered to be equally applicable to the treatment of other finely divided ore pulps.

EXAMPLE I In accordance with this invention, a calcite carrier was recovered from cassiterite in an ultraflotation froth concentrate that had been obtained by subjecting slimed vein tin ore (0.6 percent Sn) from acid igneous rock to ultraflotation with a calcite carrier and crude tall oil flotation reagent. The aqueous slimes were obtained in the following manner.

A representative sample of low grade Bolivian ore from Empresa Minera de Catavi was obtained. In addition to the small amount of cassiterite, which was the only valuable mineral in the ore, the ore contained appreciable sulfide gangue minerals, silicate gangue minerals and large quantities of quartz. The ore was artificially slimed in the following manner. 508 grams of the tin run-of-mine ore at 98.5 percent solids was ground to minus 325 mesh by crushing the ore to minus 20 mesh, and rod milling the ore for 20 minutes at 50 percent solids. The water used in the rod milling was soft water at a pH of about 7. The pH of the resulting minus 325 mesh pulp was 3.5.

Five hundred grams of minus 325 mesh tin slimes at 50 percent solids was washed and thickened by dilution to about to percent solids with soft water, settling the pulp and decanting the supernatant liquid. Before ultraflotation of the pretreated pulp to float the cassiterite, sulfides were removed from the ore by incorporating the following into the pulp in the order given: H 80 in amount of 10.0 pounds per ton; potassium ethyl xanthate, 0.25 pound per ton; and pine oil, 0.09 pound per ton. (All reagents are reported on the basis of the solids in the pulp.) After addition of the pine oil, the pulp was conditioned for 3 minutes. The pH of the. conditioned pulp was 2.6. The pulp was aerated in a Minerals Separation Airflow flotation machine and a sulfide-rich froth removed for 5 minutes. The machine discharge product at about percent solids was diluted with soft water to about 12 percent solids and agitated. The solids were permitted to settle for 60 minutes and the supernatant liquid decanted. To place the pulp in condition for ultraflotation concentration, the pulp at about 20 percent solids was dispersed in a 500 gram Fagergren cell by adding Na CO in amount of 8.0 pounds per ton of slime solids, conditioning for 1 minute and then adding 2.5 pounds of 0 brand sodium silicate per ton of solids. The pulp was conditioned for 1 minute after addition of the sodium silicate. The pH of the slimed pulp at this point of the process was 9.0. To the well-dispersed slimed pulp there was added 67.5 grams of minus 325 mesh calcite carrier having an average particle size of about 5 microns (Drikalite). The pulp was then conditioned for 1 minute. The .pH of the pulp was 8.6 and some of the slimes appeared to be flocculated. To redisperse the pulp, 1.5 pounds per ton of 0 brand sodium silicate was added and the pulp was conditioned for 1 minute.

The dispersed pulp, containing a total of 4.0 pounds of sodium silicate (hydrated basis) per ton of slime solids and about 13.5% calcite carrier (based on the slime solids) was then conditioned for minutes with an emulsified aqueous mixture containing equal parts by weight of crude tall oil and a 50 percent solution of neutral oilsoluble petroleum sulfonate in white mineral oil (Calcium Petronate). The emulsion was used in amount to provide 4.97 pounds each of crude tall oil and petroleum sulfonate solution. The pulp was at about 24 percent solids during the conditioning step. To adjust the pH of the pulp to a value previously indicated to be about optimum for flotation of the cassiterite, sulfuric acid was added as a 5 percent aqueous solution to reduce the pH of the oiled pulp to 8.2 (2.17 pounds H per ton of slimes solids). The pulp was transferred to a 500 gram Minerals Separation Airflow flotation machine and subjected to froth flotation, removing a cassiterite-rich froth product containing calcite carrier for 10 minutes. The froth product was cleaned four times by reflotation, removing a froth product for 10 minutes during each cleaner flotation. Lubricating oil (Eureka M) was added at the beginning of the first cleaner flotation in amount of 1.09 pounds per ton and an additional quantity of the oil (2.18 pounds per ton) was added at the beginning of the third cleaning.

Soft water was used throughout the process.

To separate the calcite carrier from the slimed cassiterite, in accordance with this invention, the cleaned froth product from the ultraflotation concentration was dewatered by filtration and transferred to a 1000 ml. beaker where the filtered concentrate was repulped with 600 ml. of soft water. Twenty ml. of a 5 percent solution of 0 brand sodium silicate was added while the heating and stirring was continued for another 15 minutes. Throughout, the temperature of the pulp was maintained at about F. Heating was discontinued and 5 ml. of a 5 percent solution of sulfuric acid was added, thereby reducing the pH from 9.9 to 9.1. Partial flocculation, apparently selective flocculation of the calcite, occurred. An additional 20 ml. of 5 percent sodium silicate solution was added since previous experience indicated that the use of a more dispersed pulp would give better results. The mixture was transferred to a 500 gram flotation cell and a calcite-rich froth product removed for 5 minutes. The froth was cleaned twice by reflotation and all machine discharge products were combined.

The flotation products were analyzed. The froth concentrate contained 0.10 percent Sn, representing only 3.4 percent of the tin in the ultraflotation froth concentrate and confirming visual observation that the calcite carrier had been floated selectively from the cassiterite. The combined machine discharge products contained 4.19 percent Sn, representing 96.6 percent of the Sn in the ultraflotation froth concentrate and demonstrating that the high temperature sodium silicate treatment in the presence of calcite had effectively deoiled and depressed the cassiterite. An overall metallurgical balance showed that 62.8 percent of the Sn in the original minus 325 mesh slimes was recovered.

EXAMPLE 11 Experiments were carried out to determine whether fatty acid reagentized minus 325 mesh cassiterite would be depressed by a high temperature dispersant treatment in the absence of the calcite carrier mineral. A cassiterite float product obtained from the slimed Bolivian ore with the oiling reagents of the previous example but without calcite carrier was pulped, agitated and heated with 0 brand sodium silicate for 30 minutes and then subjected to froth flotation. The results were compared to those of a imilar experiment in which a calcite carrier had been used and was present with cassiterite in the float product. The results showed that cassiterite was depressed by the high temperature sodium silicate treatment only when the calcite carrier was present, indicating hat the separation of calcite carrier from cassiterite was being realized because the calcite was desorbing the collector reagents from the cassiterite.

EXAMPLE III This example illustrates a form of my invention in which calcite is added to a rougher concentrate to desorb a fatty acid collector reagent from noncalcareous minerals in the rougher concentrate so that the rougher concentration can be further beneficiated.

A slimed rougher tin concentrate containing siliceous gangue was obtained from a sample of low grade (0.5 percent Sn) Bolivian tin ore as follows. Five hundred and eight grams of sample at 98.5% solids was wet screened through a 65 mesh screen and the plus 65 mesh fraction was ground to minus 65 mesh by grinding for three minutes at 60 percent solids. The minus 65 mesh ore was washed and thickened by dilution with soft water, settling for 60 minutes and decantation. The slimy pulp was dispersed with 10.0 pounds per ton of Na CO and 3.0 pounds per ton of brand sodium silicate. The pulp at about 20 percent solids was conditioned for 30 minutes with an emulsified mixture containing 6.2 pounds of crude tall oil and 6.2 pounds of the 50 percent solution of neutral petroleum sulfonate in mineral oil (Calcium Petronate). All reagents reported as pounds per ton of solids in the pulp. The pH of the pulp was adjusted to 8.15 by addition of 5 percent solution of sulfuric acid (1.0 pound H 50 per ton of solids). A rougher float concentrate containing 1.25 percent Sn and representing 91.2 percent of the Sn values in the ore was removed for 8 minutes.

To desorb the reagents from the cassiterite in the rougher flotation concentrate and thereby place the concentrate in a condition such that cassiterite could be selectively reagentized and floated from the silica and silicates, the rougher concentrate was processed, in accordance with my invention, as follows:

The rougher concentrate was dewatered through filtration. The filter cake was divided into two representative portions. One portion was transferred to a 2000' ml. beaker and 500 ml. of soft water was added. 67.5 grams of minus 325 mesh calcite (Drikalite) was incorporated.

Following this, 60 ml. of a 5 percent solution of 0 brand sodium silicate was added. The mixture was mechanically stirred and heat was applied. After the temperature reached 140 F., the heating was continued for 30 minutes. Temperature readings were taken at 5 minute intervals. The average reading was found to be 174 F. After being heated for 30 minutes, 10 ml. of 5 percent sulfuric acid solution was added and the mixture was transferred to a 500 gram flotation cell and subjected to froth flotation without addition of reagents. The froth product was refloated three times, producing a concentrate consisting largely of calcite. The machine discharge products were combined and found to contain 86.9 percent of the tin values of the rougher concentrate, indicating that the high temperature sodium silicate treatment in the presence of added calcite caused desorption and depression of a substantial quantity of the cassiterite in the rougher concentrate.

The other portion of the filtered rougher tin concentrate was treated in the same manner in an attempt to desorb the flotation reagents from the cassiterite, except that the calcite was added to the pulped filter cake after the pulp had been agitated with sodium silicate at the elevated temperature for 30 minutes and before aeration and flotation. Analyses of flotation products showed that a considerable amount of the cassiterite was depressed. However, the results were not as good as the results obtained when the calcite was added before the high temperature sodium silicate treatment.

EXAMPLE IV This example illustrates the use of a condensed phosphate as the dispersing agent in my process and is similar to Example I except that a solution of tetrasodium pyrophosphate was added to the tin ultraflotation concentrate and then heated to separate the tin from the calcite carrier. In performing the test, the froth product from a cassiterite ultraflotation test was dewatered by filtration and then transferred to a 1000 ml. beaker and treated with ml. of 1 percent aqueous solution of tetrasodium pyrophosphate followed by 175 ml. of soft water. The concentration of tetrasodium pyrophosphate.

was 5 grams per liter. The mixture was heated for 30 minutes at F. with continuous stirring. The pH at the end of the heating was 9.8. The pulp was transferred to a 500 gram flotation cell and subjected to froth flotation without addition of reagents. The froth product was refloated four times, resulting in an excellent separation of tin from the calcite carrier and substantially complete recovery of tin in the machine discharge product.

When the test was repeated without heating the pulp after addition of the phosphate dispersant, there was negligible concentration of the tin.

EXAMPLE V This example illustrates an embodiment of the present invention which finely divided anatase (TiO is separated and recovered from .a minus 325 mesh calcite carrier in an ultraflotation concentrate.

The ultraflotation concentrate used in this example was obtained by subjecting anatase-discolored Georgia kaolin clay to ultraflotation concentration in alkaline 23.65 percent TiO exclusive of the calcite carrier, so

that the maximum grade of the anatase concentrate obtained by high temperature silicate-treatment and flotation of the ultraflotation froth product would be 23.65 percent T-iO The procedure and reagents used to float the titania from the clay are described in Bulletin No.

M4B1l7, entitled Ultraflotation, published by Denver Equipment Company, 1400 17th St., Denver 17, C010.

In accordance with this invention, the anatase was separated from the calcite carrier in the ultraflotation froth product by filtering the froth product, transferring the filter cake to a beaker, repulping the cake with 500 ml. of 5 percent 0 brand sodium silicate and then 500 ml. soft water so that the sodium silicate concentration was 13.7 grams per liter. (46.7 pounds sodium silicate per ton of feed solids.) The silicate-treated pulp was heated 30 minutes at about 190 F. The pulp was then charged to a 1000 gm. flotation cell and frothed. The froth product was withdrawn and refloated three times. The four machine discharge products were combined and constituted the anatase concentrate. For purposes of comparison, one test was performed without heating. The results are summarized below:

Flotation separation of calcite from anatase in an ultraflotation froth concentrate by heat treatment with dispersant followed by flotation without addition of reagents Temperature of sodium Anatase concentrate, wt.

silicate treatment, F:

9. of 23.65 percent. A small amount of calcite in the an-atase concentrate would account for the lower-thanmaximum grade of this concentrate. Any residual calcite in the anatase concentrate could be removed by dissolving it with an acid.

As used in the specification and claims, the term silica refers to crystalline or cryptocrystalline silicon dioxide; silicate refers to a salt of silicic acid, especially aluminum, magnesium and mixed silicates. The term siliceous is generic and encompasses both silica and silicate minerals.

Mesh size refers to values obtained with Tyler screenscale sieves. Pulp solids are always reported on a dry basis (determined by heating the solids to constant weight at 220 F.).

The term oil is used herein to identify the collector reagents and auxiliary organic reagents employed to reagentize a pulp, and encompasses fatty acids as well as true hydrocarbon oils.

The term noncalcareous is used herein the usual broad meaning. Thus, a noncalcareous mineral is considered to be any'mineral that does not contain significant quantities of calcium. Minerals such as fluorite and scheelite would be considered to be calcareous minerals according to this designation.

I claim:

1. A method for removing fatty acid flotation reagent from finely-divided oxidized noncalcareous minerals in an aqueous alkaline ore pulp which comprises heating said ore pulp with agitation in the presence of finely-divided calcite and substantial quantities of an alkaline dispersant until the resulting froth on the surface of the pulp is clean, and subjecting the pulp to froth flotation, producing a froth product which is a concentrate of calcite and a machine discharge product which contains the finely-divided oxidized noncalcareous minerals in the desired dereagentized condition.

2. The method of claim 1 in which the aqueous ore pulp is a rougher flotation concentrate and calcite is added to the rougher flotation concentrate.

3. The method of claim 1 in which the aqueous ore pulp is a bulk float product of which calcite is a constituent.

4. The method of claim 1 in which said dispersant is sodium silicate.

5. The method of claim 1 in which said dispersant is a condensed phosphate.

6. In a process wherein a bulk float composed of finely-divided calcite and at least one finely-divided noncalcareous mineral selected from the group consisting of metal oxide and metal silicate is produced by froth flotation with a fatty acid collector reagent, a method for separating the finely-divided calcite from the remaining minerals which comprises incorporating an alkaline dispersant into a pulp of said bulk float containing fatty acid reagent, heating the pulp with agitation until the resulting froth on the surface of said pulp is clean, and without further oiling the pulp, subjecting it to froth flotation, producing a froth product which is a concentrate of calcite and a machine discharge product which is concentrate of remaining minerals.

7. The method of claim 6 in which said dispersant is sodium silicate.

8. The method of claim 6 in which said dispersant is a condensed phosphate.

9. A method for separating finely-divided calcite from slimed metal oxide minerals in a flotation concentrate containing fatty acid collector reagent which comprises forming an aqueous alkaline pulp of said flotation concentrate containing calcite and metal oxide minerals, incorporating an alkaline dispersant in amount sufficient to disperse said pulp, heating said pulp with agitation until the resulting froth is clean, and then subjecting the pulp to froth flotation at a pH of about 9.0 to about 10.0 without addition of light petroleum hydrocarbon liquid,

' sodium silicate.

11. The method of claim 9 in which said dispersant is a condensed phosphate.

12. A method for separating finely-divided calcite from slimed metal oxide minerals in an alkaline flotation concentrate containing fatty acid collector reagent which comprises forming an aqueous pulp of said concentrate, incorporating sodium silicate having an SiO /Na O ratio of 3/1 in amount suflicient to disperse said pulp and to bring the pH to about 10.0, heating said pulp at a temperature ranging from about F. to about 220 F. until the froth is clean, and subjecting the pulp to froth flotation at a pH ranging from about 9.0 to about 10.0 without addition of collector reagent, thereby producing a froth product which is a concentrate of calcite and a machine discharge product which is a concentrate of metal oxide minerals in said pulp.

13. In the flotation concentration of a slimed ore pulp to recover metal oxide mineral values wherein a slimed ore pulp is dispersed with sodium silicate, conditioned for froth flotation with added calcite and higher fatty acid collector reagent, and subjected to froth flotation in an alkaline flotation circuit, whereby a bulk froth product is obtained which is a concentrate of calcite intimately associated with slimed metal oxide minerals and a tailing composed largely of gangue minerals, a method for selectively floating the calcite from the remaining minerals in the bulk froth product, which comprises:

pulping said bulk froth product with water,

adding substantial quantities of an alkaline dispersant to the pulped froth product,

heating the dispersed pulped froth product with agitation until the resulting froth appears clean,

and, without oiling the pulp, subjecting it to froth flotation, thereby producing a froth which is a concentrate of calcite and a machine discharge product which is a concentrate of minerals originally present with said calcite in said bulk froth product.

14. The method of claim 13 in which the dispersant is sodium silicate.

15. The method of claim 13 in which the dispersant is a condensed phopshate.

16. A method for separating minus 325 mesh metal oxide minerals from gangue including an appreciable quantity of minus 325 mesh calcite which comprises pulping the mixture and subjecting the pulp to froth flotation in an alkaline circuit in the presence of a fatty acid collector reagent, thereby producing a bulk float product which is a concentrate of calcite and metal oxide and a tailing composed largely of gangue, incorporating an alkaline dispersant into a pulp of the froth product and, while the pulp is alkaline, heating it with agitation until froth on the surface of the agitated pulp appears clean, and subjecting said pulp to froth flotation without addition of collector reagents, thereby producing a machine discharge product which is a concentrate of metal oxide minerals and a froth product which is a concentrate of calcite.

17. A method for separating finely-divided calcite from a finely-divided anhydrous oxide of a tetravalent metal in an aqueous alkaline pulp containing fatty acid collector reagent which comprises adding an alkaline dispersant to the pulp and heating the pulp with agitation until the froth on the surface of the pulp is clean, and without oiling the pulp, subjecting it to froth flotation, producing a froth product which is a concentrate of calcite and a machine discharge which is a concentrate of said finelydivided anhydrous oxide of a tetravalent metal.

18. The method of claim 17 in which said anhydrous oxide of a tetravalent metal is TiO 19. In the flotation concentration of slimed cassiterite from a slimed ore pulp obtained from acid igneous rock wherein slimed ore pulp is alkalized and dispersed with sodium silicate, conditioned for flotation of cassiterite by incorporating minus 325 mesh calcite and tall oil, and subjected to froth flotation in an alkaline circuit, producing a froth product composed largely of calcite intimately associated with slimed cassiterite and a tailing which is a concentrate of slimed gangue in said ore pulp, a method for separating calcite from the remainder of the froth product and recovering the cassiterite which comprises:

dispersing an aqueous pulp of the froth product with sufficient sodium silicate to bring the pH of the pulp to a value ranging from about 9.0 to about 10.0, heating the pulp at a temperature Within the range of from about 150 F. to about 220 F. for a time ranging from 10 minutes to 2 hours, the time being sufficient for the froth on the surface of the agitated pulp to become clean and, without adding a collector reagent, subjecting the pulp to froth flotation, thereby producing a froth product which is a concentrate of substantially pure calcite and a machine discharge product which is a concentrate of slimed cassiterite.

20. In a process for removing titania from kaolin clay containing titania as a finely divided impurity by subjecting a dispersed aqueous pulp of said clay containing titania impurity to froth flotation in the presence of a fatty acid collector reagent and finely divided particles of calcite as an additive to the clay in the pulp, producing a froth product which is a concentrate of titania originally present with the clay in intimate association with the calcite additive and machine discharge product which is a concentrate of clay,

a method for separating said calcite from said titania in the froth product and recovering the calcite and the titania which comprises incorporating an alkaline dispersing agent into a pulp of said froth product,

heating the pulped froth product with agitation until the froth on the surface is clean and, without addition of oiling reagents, subjecting the pulped froth product to froth flotation, producing a froth product which is a concentrate of the calcite and a machine discharge product which is a concentrate of'titania.

References Cited HARRY B. THORNTON, Primary Examiner.

R. HALPER, Assistant Examiner. 

1. A METHOD FOR REMOVING FATTY ACID FLOTATION REAGENT FROM FINELY-DIVIDED OXIDIZED NONCALCAREOUS MINERALS IN AN QUEOUS ALKALINE ORE PULP WHICH COMPRISES HEATING SAID ORE PULP WITH AGITATION IN THE PRESENCE OF FINELY-DIVIDED CALCITE AND SUBSTANTIAL QUANTITIES OF AN ALKALINE DISPERSANT UNTIL THE RESULTING FROTH ON THE SURFACE OF THE PULP IS CLEAN, AND SUBJECTING THE PULP TO FROTH FLOTATION, PRODUCING A FROTH PRODUCT WHICH IS A CONCENTRATE OF CALCITE AND A MACHINE DISCHARGE PRODUCT WHICH CONTAINS THE FINELY-DIVIDED OXIDIZED NONCALCAREOUS MINERALS IN THE DESIRED DEREAGENTIZED CONDITION. 